When two optical fibers are spliced, in particular welded to each other, melt-fusioning by means of an electric arc is often used, but also other heating methods can be used for the fusioning, such as heating by means of a thermal heat ray or beam from a carbon dioxide laser. Further, different methods of pre-treatment for preparing the optical fibers for splicing are used and these methods comprise removing the polymer coating and other possible coverings and also dirt and particles attached to the surface of the optical fiber. Optical fibers of type single-mode having a standard diameter of 125 m normally have a tensile strength of about 70-80 N. Such a high tensile strength is normally not achieved in welded splices between optical fibers but the values of the tensile strength can be as follows:
______________________________________ Fiber end Tensile strength of preparation Fiber splicing splice ______________________________________ Normal mechanical Normal fusion 3-7 N stripper splicing Non-contact Normal fusion 10-20 N mechanical stripper splicing Non-contact acid Normal fusion 20-30 N stripper splicing Non-contact acid Splicing with arc 30-60 N stripper initiation when ends are remote Original optical No splice 70-80 N fiber ______________________________________
A prior splicing method performed by igniting an electric arc or generally by starting the heating within a localized region, when the ends of the fibers are located at a distance therefrom and by then moving the fiber ends into the hot region where the heating is intensified more, so that the fiber ends are melted and then are fused together ("Remote Arc Initiation Method"), gives the achieved splice very good tensile strength values. Such high tensile strength values are in particular desired for fibers used in difficult environmental conditions such as for fibers in optical fiber cables used under water or for fiber devices to be used in military applications. However, when using this splicing method a relatively large and uncontrollable loss or attenuation of the transmitted light is obtained in a spliced fiber. This depends on the fact that the fiber ends have to be moved back to the actual electric arc region in order to make it possible to perform the fusioning and the fact that in this movement the alignment of the fiber ends with each other will not be good or will be lost, mainly depending on mechanical imperfections of the mechanical control and guide means and on the fact that electric or other forces from the electric arc itself can affect the free portions of two fiber ends in different ways, so that they may be somewhat bent or deflected from their original non-influenced state. The alignment error can be as large as 10 m when the fiber ends get in contact with each other and the fusioning begins. Such an alignment error can in turn result in a loss in the splice comprising up to 0.5-1 dB. A loss of this magnitude is not acceptable in many applications.